High-Throughput Sequencing Investigation of Bacterial Diversity in Chronic Suppurative Otitis Media and Middle Ear Cholesteatoma

Abstract

Background. Chronic otitis media is a common middle ear disease in otolaryngology. Bacterial infection is considered as the cause of the disease, but relying on conventional bacterial cultures can be problematic for identifying specific pathogens. Current research suggests that bacteria in microbial communities can only be identified by rDNA sequencing of bacteria. Methods. This cross-sectional study utilized broad-range PCR amplification of 16S rRNA genes with clone analysis to compare bacterial diversity in lesions from 6 patients with chronic suppurative otitis media (CSOM) and 10 patients with cholesteatoma of middle ear lesions. Bacteria were analyzed at the levels of phylum, order, family, genus, and species. Results. The age and sex difference between the patients with chronic suppurative otitis media and the patients with middle ear cholesteatoma were comparable ( $P>0.05$ ). Bacterial species abundance and species diversity were greater in cholesteatoma of the middle ear lesions than in CSOM lesions. The total number of detected operational taxonomic units (OTU) was 838, comprising 788 OTU detected in cholesteatoma pathological tissues, 230 in CSOM pathological tissues, and 180 OTU common to both groups. Proteus is a major part of CSOM (99.46%, $P=0.000321$ ). The phyla detected in the Cholesteatoma samples were Proteus (Proteobacteria) (35.77%), thikum (Firmicutes) (44.21%, $P=0.001071$ ), and Actinomycetes (Actinobacteria) (16.66%, $P=0.032464$ ). At all bacterial taxonomic levels, the epithelial tissue of middle ear cholesteatoma was complex in terms of bacterial diversity, covering many Gram-positive and Gram-negative bacteria, likely related to bacterial microbiome formation. In contrast, the bacteriology of the CSOM lesions was relatively simple at all taxonomic levels, with all sequences characterized as belonging to Gram-negative bacteria. Conclusion. Our results suggest that persistent middle ear cholesteatoma infection may be a microbial flora disorder related to conditional pathogenic bacteria rather than a single bacterial infectious disease. The pathogen is relatively single in the diseased tissue of chronic suppurative otitis media, which is the main reason for its effective antiinfection treatment.